The present invention relates to data processing apparatuses which include preprogrammed complex number arithmetic functions. This functional capability is most often found in the so called "scientific calculators". These calculators generally include a wide variety of functions in addition to the four basic arithmetic operational functions of addition, subtraction, multiplication and division. These machines typically include a keyboard for entering information and operational commands into the machine and a visual display for communicating an indication of the results to the operator. These machines often include a plurality of user accessible memories. A user acessible memory is a data memory which the operator can selectively address for both storing and recalling data. A user accessible memory may be used for a store operation in which a displayed number is stored in a selected memory, a recall operation in which the number stored in a selected memory is displayed or an exchange operation in which the displayed number and the number in a selected memory are exchanged. Typically, storing and/or recalling data in one of these machines requires a two key stroke sequence, the first sequence indicating the specific store, recall or exchange operation desired and a second key stroke used to designate the particular memory addressed. Such a machine may also include a provision for memory arithmetic as described in the copending U.S. patent application Ser. No. 280,640, of Caldwell et al, entitled "Data Processing Apparatus with Algebraic Memory Operation and Entry Sequence", filed July 6, l981 allowed Issue Fee paid May 17, 1984.
A problem exists with this type of calculator organization. Firstly, provision of complex number arithmetic functions in such a calculator is not typical. In those calculators in which such complex number arithmetic is supported, the user is often required to enter the parts of the complex number into specifically designated user accessible memory so that the calculator may recall these parts of the complex number in carrying out designated complex number arithmetic.
This type of organization requires concentration of the user to remember, firstly the particular user accessible memories to which each portion of a complex number must be stored and secondly requires the user to know the particular portions of the user accesible memory where the separate parts of the computer results of the complex arithmetic are stored. Typically such a calculator does not give the user any indication of when the calculator is in a complex number computation mode, nor does the calculator give the user any indication of which part of a particular complex number is indicated by the display. Thus much of the usefullness of a calculator in this form of computation is negated by the requirement that the user keep track of many of the functions involved in the complex number arithmetic.